CAN BUS · HARDWARE IN THE LOOP

CAN Bus HIL
Test System

A physical Hardware-in-the-Loop test bench built with BeagleBone Black and ESP32, communicating over CAN bus at 500 kbps — verified with Saleae Logic Analyzer.

500kbps bitrate

16/16tests passed

0CRC errors

<1msround-trip

Concept

What is HIL?

Hardware-in-the-Loop (HIL) is a test methodology where real hardware is validated against simulated signals — mirroring how Volvo Cars, Bosch, and Continental verify ECU behaviour before integration with physical actuators.

Master

BBB

Sends test commands, validates responses, logs results

Slave

ESP32

Simulates an ECU — processes commands, replies over CAN

Protocol

CAN

Physical bus, twisted-pair, 120 Ω termination both ends

Verification

Saleae

Logic Analyzer — CAN protocol decoder, 500 kbps

Hardware

Components

All components breadboarded with twisted-pair CAN cable and 120 Ω termination at each end of the bus.

Component	Role	Interface	Voltage
BeagleBone Black	HIL Master — SocketCAN / C	P9_19 / P9_20	3.3 V
ESP32	HIL Slave — TWAI driver / C++	GPIO4 / GPIO5	3.3 V
SN65HVD230 ×2	CAN transceiver — no level shifter needed	Differential	3.3 V
120 Ω resistors	Bus termination — both ends of CAN line	CAN-H ↔ CAN-L	—
INA219	Power monitor — current & voltage measurement	I2C	3.3 V
Saleae Logic Analyzer	Signal verification — CAN protocol decoder	Tap point on CAN-H	Passive

Wiring

Connections

Both SN65HVD230 transceivers share the same CAN-H / CAN-L twisted-pair bus. Termination resistors sit at the outermost nodes.

Wiring diagram — ASCII 500 kbps · twisted-pair · 120 Ω each end

BeagleBone Black SN65HVD230 #1 P9_20 (CAN0 TX) ──────────► D P9_19 (CAN0 RX) ◄────────── R P9_3 (3.3 V) ──────────► VCC P9_1 (GND) ──────────► GND │ CAN-H ──[120Ω]───────────────────── CAN-H CAN-L ─────────────────────[120Ω]── CAN-L │ ESP32 SN65HVD230 #2 │ GPIO4 (TX) ──────────► D ──┘ GPIO5 (RX) ◄────────── R 3.3 V ──────────► VCC GND ──────────► GND

Protocol

Message Format

Standard 11-bit CAN frames. BBB sends commands on ID 0x100; ESP32 responds on ID 0x200.

BBB → ESP32 · Command frame · ID 0x100

Byte 0CMD code

Byte 1VALUE high byte

Byte 2VALUE low byte

Bytes 3–7Reserved 0x00

ESP32 → BBB · Response frame · ID 0x200

Byte 00xFF OK / 0xEE ERR

Byte 1CMD echo

Byte 2VALUE high byte

Bytes 3–7Reserved 0x00

Test Scenarios

Validation Cases

Four scenarios run in a continuous loop with 1-second timeout per frame and automatic pass/fail logging to hil_log.txt.

CMD 0x0F

Heartbeat

Connection check — verifies CAN link is alive between master and slave.

→ RESP 0xFF OK

CMD 0x01

Engine RPM

Sends RPM (0–8000). Out-of-range values return 0xEE error.

→ 3000 RPM · 0xFF OK

CMD 0x02

Fuel Injection

Sends injection duty-cycle value. Slave acknowledges control command.

→ 0x1F · 0xFF OK

CMD 0x03

Temperature

Sends coolant temp (0–150 °C). Over-range triggers error response.

→ 85 °C · 0xFF OK

Logic Analyzer

Signal Capture

CAN bus signal captured on CAN-H line using Saleae Logic 2 with the CAN protocol decoder active at 500 kbps, 87.5% sample point.

Saleae Logic 2 · CAN decoder · D0 channel · 2 MHz sample rate 500 000 bps

Logic analyzer capture showing CAN frames 0x100 and 0x200 with protocol decode

0x100 BBB → ESP32 command frame

0x200 ESP32 → BBB response frame

~50 ms frame interval

~1 s test cycle

CRC-15 no errors detected

87.5% sample point

Output

Test Log

Automated pass/fail log generated on BeagleBone Black. Full log saved to hil_log.txt.

root@BeagleBone:/home/debian/hil_project — ./hil_master can0

===========================================

HIL Master - BeagleBone Black

CAN Bus HIL Test Sistemi v1.0

===========================================

[11:10:49] HIL Master baslatildi - can0 @ 500kbps

--- Test Turu 1 ---

[11:10:49] GONDERILDI: [Heartbeat] CMD=0x0F VALUE=0

[11:10:49] BASARILI: [Heartbeat] ESP32 cevabi OK

[11:10:50] GONDERILDI: [Motor RPM 3000] CMD=0x01 VALUE=3000

[11:10:50] BASARILI: [Motor RPM 3000] ESP32 cevabi OK

[11:10:51] GONDERILDI: [Yakit Enjeksiyonu] CMD=0x02 VALUE=31

[11:10:51] BASARILI: [Yakit Enjeksiyonu] ESP32 cevabi OK

[11:10:52] GONDERILDI: [Sicaklik 85C] CMD=0x03 VALUE=85

[11:10:52] BASARILI: [Sicaklik 85C] ESP32 cevabi OK

[11:10:53] OZET: Toplam=4 Basarili=4 Basarisiz=0

--- Test Turu 2 ---

[11:10:55] GONDERILDI: [Heartbeat] CMD=0x0F VALUE=0

[11:10:55] BASARILI: [Heartbeat] ESP32 cevabi OK

[11:10:56] GONDERILDI: [Motor RPM 3000] CMD=0x01 VALUE=3000

[11:10:56] BASARILI: [Motor RPM 3000] ESP32 cevabi OK

... (continuing)

[11:11:12] OZET: Toplam=16 Basarili=16 Basarisiz=0

Results

Test Report

All four test scenarios passed across multiple continuous test cycles with zero errors.

16/16 test scenarios passed

0 CRC errors detected

500k bps stable bitrate

<1ms round-trip latency

↗ View full source on GitHub — bahadir2/hil_project